while not impossible, it is improbable we are looking at 2002 with changed nose. as far as i know, usual procedure, seen with pretty much all other development programmes uses the first two or so airframes for basic flight testing only. there are no plans to put radar on them, ever. and thus the nose structure is different, even if outside design is the same. those planes never carried radar, until their retirement. so while it is possible to cut the nose section and restructure it so a radome can be placed there, i don't know if such a move was ever done for any similar fighter programme.
Assuming we are looking at the third prototype, let us compare it with other programmes:
j20
first airframe first flew: january 2011
second: may 2012
third: november-december 2012 ???
IF the third one does fly in the next month or two, which seems quite possible, we will be looking at second airframe flying 16 months after first and third airframe flying 22-23 months after first one.
pak fa
first airframe: 19 january 2010
second: 3 march 2011
third: 22 november 2011
pak fa programme had second airframe fly 13-14 months after first and third one 22 months after first one.
f22
first flying prototype first flew: september 7, 1997
second flying proto flew: june 29, 1998
third flying proto flew: march 6, 2000
fourth flying proto flew: november 15, 2000
fifth flying proto flew: january 5, 2001
sixth proto flew: february 5, 2001
seventh proto flew: october 15, 2001
serial standard planes first flew in second half of 2002.
f22 programme had second airframe fly 9-10 months after first one. third airframe flew 31 months after first one.
f35
first flying proto: december 15, 2006
second flew: june 11, 2008
third: february 25, 2009
fourth: november 14, 2009
fifth: february 2, 2010
sixth: feb 7, 2010
seventh: april 20, 2010
f35 programme had second airframe fly 18 months after first. third one flew 26 months after first one.
typhoon
first flew: 27 march 1994
second: 6 april 1994
third: 4 june 1995
fourth: 31 august 1996
fifth: 27 january 1997
sisxth: 24 februrary 1997
sevent: 14 march 1997
april 2002: three IPA planes flew
februrary 2003: first production plane flew
typhoon programme had two "first prototypes". Third airframe flew 15 months after them. The following one flew 28 months after the first one.
j20 seems to be on track quite nicely. we should see the next prototype in the air sometime in the summer of 2012, possibly early autumn. After that we might see next few remaining prototypes fly shortly one after another, perhaps all of them during winter/april of 2013. Then the big question is how will the prototype quality transfer into production line examples. best case scenario might be that early 2014 is when first preproduction batch will start. Realistically though, that is the period when a good deal of problems might arise. So instead of preproduction batch ending in early 2015, we might see it being protracted to sometime in 2016. That, however, is still well inside the projected service entry window as first production batch, even if started in late 2016., should be enough so large scale training is done during 2017. and most of 2018. and first squadron enters service before the end of 2018. Eight years total, with one year being there because of unforeseen consequences. Without it, even a 2017. entry into service is possible.
then again, we might see a f35 or typhoon kind of schedule - where all bets are off.