People often bring up the idea of all of invite refusing to play in some attempt to force ESEA's hand, which sounds ridiculous on paper. However, it's unclear as to what would actually happen in that scenario (assuming it's even a possibility in the first place)
The biggest concern is that ESEA will drop TF2, but that wouldn't be the end of the scene all at once. You still have a tight-knit community with hundreds of people eager to play and plenty of alternative leagues to accommodate them.
LAN is obviously ESEA's biggest draw right now, and nobody really wants to go without it. Even so, I doubt much of invite will quit right away if it doesn't happen for a season or two. It's a huge financial hassle for the invite teams attending and only one of many goals for those who aren't.
If anything the casting staff of TF.TV and VTV are the ones hurt most by the absence of LAN, considering how important high-quality casts of star-powered matches are to growing the game. Covering a big event like LAN from season to season is what brings the community together and draws in new players, and the loss of that opportunity is what we should be most concerned about should LAN not happen. It's unlikely that any of the alternative leagues will be able to provide a LAN event any time soon, but that doesn't mean they shouldn't be considered at all.
The alternative leagues might look dinky compared to ESEA right now, but take a moment to consider what it would be like if you ran one of them and ESEA stopped being an option. Suddenly there's a HUGE untapped market in the displaced community, and it's up to you to provide the highest quality league around or lose all those numbers to the guys that do. Competition like that is what the community needs in its leagues, else you get something like, well, ESEA.