We have all come to be familiarized with TF2′s 6v6 format and its intricacies, and it was decided upon after quite a bit of community testing. However, is this ideal?
The main advantage of 6v6 is that it allows for a great depth of teamplay while also retaining some significance to individual abilities (and those not being overshadowed by other variables, such as spam and numbers) and it plays at a good pace.
However, when most people discuss TF2′s format or propose changes, it is nearly almost always 7v7, 8v8 or 9v9 highlander. Indeed, this only worsens the problems of 6v6, and this is why I think it could be time for further experimentation in the direction of 5v5.

Why 5v5? Well, the reason being that individual abilities shine further, allowing for more clutch moments that spectators love and that can look impressive to potential sponsors. Additionally it is far more convenient, as the ease of finding a 5th player is greater than finding a 6th (and particularly when you bear in mind that starting from the 1st player to the nth player, each subsequent player will have to fit in with the ones before him). Then there is a matter of logistics and sponsorship, and the simple furthering of TF2 competitively. It would be cheaper for sponsors to provide LAN support for 5 players
On top of this, any prize pool will only be split over 5 players, and thus individual prizes will automatically increase. And as such, it might aid in furthering TF2 competitively for future LANs, one-night cups and other prize events.

And finally, one of the greatest strengths of 5v5 is that there will be a greater abundance of teams. For every 5th team we have today, there could be a new team. It would further team diversity more, and we might be able to have more top teams that are closer to 1st place, and I think this is one of the main advantages of going 5v5.