Kavwell realistically making a sequel would likely be more feasible than undertaking the massive optimization, rebalancing, and rebranding that tf2 would need to really compete as a high end esport these days. tf2 has a serious reputation as a pub game and hat simulator on top of needing a lot of work anyway; and if valve really cared about making it into a profitable esport itd probably be more successful as a sequel rather than an improved tf2.
I agree tf2 should be treated like CSS and valve should just put out a 'sequel' which is more competitively viable, like CSGO was for the cs series. Remove unnecessary items, allow every player access to crucial weapons and revert some balance changes. Then price the whole thing at 15-20$ and add skins without ruining performance (maybe no hats to preserve the recognisability of the different classes). Finally, push it a bit as an esports and enjoy profit :) .