If miners decide to fork it, they'll have created a precedent of zero trust in future stability. Why would BTC continue its existence as a store of value when everyone knows it has and it can be forked in the future into multiple currencies?

It all comes down to miners and whether they like mining 400$ BTCs or if they'd like 100$ gavincoins - after the fork, destroying BTC and their own business as well.

Not raising the block for a little while longer, will at most prevent some spam and dust transactions and raise the fees a bit. It's 3-8 cents right now for first block inclusion while the largest portion of transactions are paying near the minimum to avoid costs and don't care for speed at all.

Forking the currency is destructive for everyone. If the miners like to wear a dynamite vest and blow everything up like suicide bombers, well, we'll have to see what happens next.

Personally I'm not discounting the possibility of satoshi returning to officially declaring it a failure and disassociating himself from the post-forking power grab.