SOURCE: REDDITOR senaya
Regarding penetration: they are considering the worth of intentionally lowering pen of all of the guns, reworking pen system from scratch and changing how gold ammo is working.
Regarding the engine: half of it is already changed (since 9.9) and Big World will completely dissapear from our clients by the end of the year. Also, multicore support is in a very early stage.
Regarding premium arty: nay for now, but after a (long) while it might become available as a reward for a bunch of missions, marathons or w/e.
Regarding tier12 tanks: there is a special mode with a modified matchmaking that will allow both sides (tier10 players and tier12 players) to have their fun. This mode is still in the works and can even be scrapped entirely.
Regarding DirectX12: on a much later date, not in 2015 for sure.
Regarding new physics: tanks falling on a side will get rolled back (He used “обратно” so I guess it’s “back on tracks”). Also, new spots that became available after the introduction of new physics are breaking their already fragile map balance.