That is a very reasonable prognosis, remembering that they still have to deliver most Lot 06 J-10A's in 2012.If China stands up a Regiment of J10B every year from next year by 2020 that will be 8 Regiments thats 224 aircraft, similar to what J10A numbers are right now, which isnt that bad, also by 2020 J20 will be in production and good medium-high end mix will be fine for China
Considering J10B will be in service for decades to come a few years late wont make any difference
can J10A be upgraded to J10B standard in the future?
An yes, of course they will be in service for decades to come. Modern combat aircraft should be expected to serve for nearly 40 years, and the J-10 only entered front-line service (with 131 Regt, 44 Ftr Div) in 2004