ArxPheeshArx I think one thing you are discounting is assuming that valve would not respond to overwatch w/ prize pools of their own. There's no doubt in my mind if blizzard goes hard at competitive with large prize pools etc then Valve will respond w/ TF2 in the same way. I think the main reason they have not done that w/ TF2 is that there has been a disconnect between the competitive play and pub play. Matchmaking will finally bridge that divide between casual and competitive scenes which imo is a huge deal for their future support of the scene. Look at what they did w/ Dota to compete w/ LoL. They aren't just going to sit idly by and let blizzard take player share. :)
People SHOULD go to overwatch if it has more support in the competitive scene, even if they love TF2. If nothing else it forces Valve to up its support in kind. If Valve fails to respond then you picked the better option anyway.
The problem is, TF2 is a really old game now. It would be really stupid for Valve to throw money at an old game to save a handful of competitive TF2 players. You have to remember that Valve is a business and while the whole TF2 competitive community wants these big prize pools, weekly leagues and tournaments, we simply do not have the player-base in the competitive community to warrant it.
Everyone knows about TF2. It's a free game and so a tonne of people have played the game and enjoyed it. It's not like you're suddenly going to getting a massive influx of players just by adding some money to it. The only way that TF2 can grow is the way it has been growing for a while; through slow and steady community efforts and frequent game updates / content. The issue with this is that at the same time that new competitive players join the scene, old ones are leaving for new games, or to move on with their lives. This has kept the TF2 scene pretty constant in size. I mean... if you add all the players who have retired back into the scene, TF2 would be absolutely massive, but sadly that isn't the case.
Valve do not even need the competitive scene to continue with TF2. We are a small form of advertising for them with our tournaments and articles, so it is worth doing a few things for us (such as adding some things to the game and some balance changes), but the majority of their money comes through public players, traders and crafters. It's better for them to spend their resources to satisfy those people and sadly there are much more cost effective ways than to throw 5 figure sums at a 6vs6 prize pool.
Overwatch is new. Players will play it. It's worth throwing money at it at the start to get people to play the game and potentially become another eSports title for Blizzard. They will invest heavily in the game and if enough people jump on board, they will continue to invest in it. Valve simply will not be willing to plough in that same level of investment. The best thing that Valve could do at this point is to let Blizzard invest in OverWatch and then introduce a TF2 sequal that can steal the overwatch player base further down the line. All speculation of course as I'm not Valve, Blizzard, nor do I know how they run their businesses.
Parts of what you said I aren't exactly correct. Valve aren't making matchmaking to appease the competitive community, they are doing it out of an incredibly large shift in player habits. The days of community servers are pretty much over and party matchmaking is key for any games success. This is why Valve is adding it in to the game, they are just using 6v6 as a baseline and will probably make the changes that they feel it needs.
Other things to take in to account is that Overwatch has no pre existing player base to cater too, there isn't an ageing game for it to really replace, the only similarities that TF2 has to Overwatch is that it's class based, it looks like a completely different game in many aspects.
And Valve will be willing to put the investment in this game if it's worth the return, TF2 at i55 had really good numbers, some of the Heroes of the Storm tournaments (Not a good comparison but it's the only other team based game Blizzard do that they've been throwing money at) has pretty shit numbers considering how much work they are throwing at it.
Just because Blizzard are going to be throwing money at the game doesn't mean that everyone is going to flock over to them, Blizz are becoming incredibly shaky with their new IPs and drawing in player numbers and I don't think this game will be any different, their most successful games all come from existing IPs again.
And finally, as Pheesh has said, they really don't need to plug in their own money a whole lot, Dota2 tournaments pretty much live off crowd funding stuff and referring to TI5, I think valve only put what? $1,5 Million? And it went all the way to $18 Million.