Is it possible to discuss an increase of transaction fees for small miners? On "big" cryptocurrency related news websites they write about this possibility, but I guess it will be not interesting at all for the major part of small miners.

Regarding the future of "big miners", - you surely know that in Irkutsk (Russia) a russian oligarch pays near 0.2 RUB per kWh (for today: 0.0027 USD) for an electricity for his big farm. Surely it remain effective to mine and for the future.