Lets check your list, what India will have in 2020
1. 272 SU-30MKI ----> Yes
2. 126 MMRCA ----> Yes (may be more than 126)
3. 51 upgraded mirage ----> Yes
4. 250 PAKFA -----> No (as it will start coming only in 2017)
5. 250 LCA ---> LCA (will definitely come, not sure abtout numbers)
6. 78 mig 29 ---> Yes (may be more of the advanced version)
7. 45 mig 29K (Navy) ---> Yes
8. 100 mig27 ----> Yes (they are upgadred but by 2020, we may have 60 odd mig27)
9. Mig23 ----> No (All ready phased out)
10. Mig21 bison ---> No (will be phased out by 2020)
11. Jaguars ---> Yes (You forget to mention it.)
As indianrabbit said, those 2 MKI should be replacements for those that was lost in accidents, so 270 MKIs.
126 MMRCAs are doubtful till 2020, going by a similar production rate as we saw at MKI, I would say 18 + 60 licence produced.
FGFA, hardly 1, or 2 squads in that timeframe.
LCA should be less too, 40 x MK1 and 100 to 150 MK2 at max till then.
Mig 27 will be phased out and mainly replaced by MKI, only 2 squads (32 fighters) were upgraded and the only Mig 23 that are in service are used as Mig 27 trainers.
Mig 21 Bisons will be replaced squad by squad with MMRCA winner, so they might need a bit more time to replace them all.
Although all reports hints that 100 Jags will be upgrade, it will be interesting to see if IAF really want's that. They are dedicated strike fighters and might be only useful in large numbers, if we take an MMRCA with less developed A2G capabilities (EF, Mig 35, Gripen NG). Otherwise they will only stay in reserve for war times, because be it F16 IN, Rafale, F18SH, as well as present MKIs, or upgrade Mirage, they all are more capable than the Jags.