I don't know. I found a comment on a livejournal photo report. The guy asked the officer on the base about their Su-27SM aircraft. He got the answer that these weren't SM, but more advanced SM2 aircraft. No details followed.@Feanor: You correctly understood the article. Wikipedia also doesn't mention any differences between SM1 and SM 2 standard.
How is it with the Su-27 upgrades? Does the Su-27SM2 differ from the SM 1 variant?
Originally the SM2 was a speculated (possible proposed) upgrade that involved retrofitting most systems off the Su-35S on to the Su-27 airframe. However no real info on it ever materialized.
So, the truth is I have no idea. It might be something different.
I'll look it up, but entry into service is rarely decided in advance, so all you can get is an expected date. Actual entry into service depends on completion of state trials, and sometimes on experimental exploitation results. Deliveries on the other hand are to start next year. Entry into service can involve pre-production aircraft completing trials, or it can happen after multiple squadrons are in service and even performing combat (the prime example being the Su-34).What I also couldn't find out is when the Su-25UBM will finally enter service. Sukhoi has been working on it for several years so it should be ready soon.
This is mostly a product of the post-Soviet disintegration of the armed forces, and the procurement organization. So yeah.