I think that the period of late 2002 to 2007 was probably China's first naval shipbuilding boom. During that period, we saw a lot of new platforms introduced like the new DDGs(051C,052B/C), new FFGs (054, 054A) and even larger ships (like replenishment ships and Type 071 LPD). After that, we had a couple of years in 2008 and 2009 where we had a lull and only saw the end of the 022 production run, numerous 054As and some Yuan coming out. The only new ship we saw were the large hospital ship and the new submarine tender.
Part of the reason for this slow down was the move of JiangNan shipyard to ChangXin and changes in other major shipyards. A larger reason for this is the raw number of new hardware coming into service that was simply overwhelming PLAN's ability to absorb them. A final reason is the PLAN philosophy in introducing new platforms. They typically make a huge leap in the first prototype while continuing to building ships of existing variant. Once they sort out all of the problems in the first prototype, they start to mass produce this new class. As they mass produce, they continue to make smaller tweaks until the end of the production run. A typical example of this is the 054 series. They commissioned a pair of 054s in 2004, but they built 2 more older Jiangwei class frigates after that. By 2006, they started to mass produce the improved variant 054A. They have made a couple of small changes after the first 4 054As, but the production run have generally remained constant throughout the past 4 years. We have seen 10 054As appearing by now. In some cases like 022, they built the first 4 units and it did not take very long before they really started cranking them out.
And finally, there are the destroyers and the amphibious ships. 052C was a huge technology leap from what China had before. The jump was so huge that PLAN did not order another 052 series DDG until the current DDGs under construction in JiangNan (a span of 5 years). Type 071 LPD is another example where the leap was huge. The first ship 998 was commissioned by late 2007, but we only started seeing the second unit under construction in the past few months. They took a long time to learn how to operate a much larger amphibious ship with support for multiple helicopters and LCACs. I believe that we have really entered a second shipbuilding boom for PLAN, because mass production has started for some of those prototype units they built in the first period of boom.
The most interesting case study is probably PLAN's conventional submarine program. They built the first song submarine 039 in 1994. Even though it was not very advanced, China was so technologically backward back then that it didn't enter service until 5 years later. They made several changes and commissioned 3 of these modified Song (039G class) submarine from 2001 to 2003. They made some more smaller changes and really mass produced 9 to 12 of these improved Song (039G1 class) submarine from 2004 to 2006. These are currently the workhorse of PLAN. At the same time, they launched the lead unit in the Yuan (039A class) submarine in 2004, which probably commissioned in 2006. I would say that the technological leap from 039G1 to 039A was not all that great, but it still took them 3 years before we saw the next Yuan submarine coming out. The next 3 Yuan submarine launched in 2007 and 2008 were slightly modified from the first Yuan, so we could call that 039A1. The interesting part is that we did not see any more photos after the early part of 2008 of new unit (at least none that we were sure about). There was possibly one as shown below, but I'm not 100% sure.
While this was happening, I heard a lot of rumours that there were a bunch of new submarines under construction at WuChang shipyard. This was obviously verified in the past month when we saw that mysterious new diesel submarine showing up. I've been calling it 039B, but PLAN probably has a different designation for it. It probably represents a much larger evolution in technology over Yuan compared against Yuan's evolution from Song. So, I would say that this submarine is in the same position that Yuan was in 2004 to 2005. Another similarity is that Yuan submarines are still getting pumped out. These are a couple of pictures that shows the new submarine with a Yuan class submarine in the background. I do find the submarine in the background to be slightly different from the previous Yuan submarines (as shown in the first photo). The front top edge of the sail seems to be curved and it's also hard to see any torpedo tube launchers. If we look at the second photo (which gives a better prospective of the sizes), I would say that the new submarine has much longer sail and is probably a little larger too. Since Yuan is already quite a large conventional submarine, the new one seems to be designed to be quite an ocean going submarine. It's quite possible that we've had a couple of other units of this slightly modified Yuan submarine built in the past 2 years, but the pictures from WuChang shipyard don't come out as often. We know that JiangNan shipyard has started to crank out naval vessels again, so both WC and JN are probably building Yuan submarine at this point. It's the same scenario that we had in 2004/2005 with Song and Yuan. At that point, we were seeing 3 or 4 submarines coming out each year for a 3 years production run. That probably would not happen this time around, but we will probably see mass production of the latest variant of Yuan until the new submarine is ready for mass production.