Production of the Su-57 is supposed to increase further after the Su-57M passes trials and is approved into production. Plus it is not like KNAAPO is the only aviation factory in Russia. KNAAPO produced the Su-35, but they also have the factories which build the Su-30 (Irkut), the Su-34 (NAPO), and the MiG-35 (Sokol). All the Flanker factories could likely be converted to produce Su-57 variants if they wanted to. It is just that Irkut and NAPO are supposed to be busy upgrading aircraft to Su-30SM2 and Su-34M status. Sokol still has not got a further order for the MiG-35 and I doubt they still have that many MiG-31 to continue to upgrade to MiG-31BM or MiG-31K. Right now Sokol are only testing out a fly by wire system for the MiG-31. The PAK-DP will only arrive in the end of the decade if at all.
If it was me I would not bother upgrading the Su-30s. The current upgrade is kind of lame anyway since it seems they are not putting the Irbis-E radar in them as planned. Instead I would just convert the facilities at Irkut to produce Su-57Ms. As for the Sokol plant, I would just switch it over to produce the Su-75 whenever that becomes available.