don't be naive the 5 central devs could pretty much do what they wanted (gavin's even openly says this),
now the argument that majority wouldn't follow a bad play....well that could be valid if 1) the majority aren't apathetic AND 2) the majority understand the change and consequences (they'd believe the devs over and above the vocal few expressing the opposite view) AND 3) the majority had bitcoins best interest at heart rather then their own personal fiat gain.
becomes like fiat majority learn its dodge they'd still try and keep it in play for fear of system collapse.
you really think bitcoin would survive a split between the core devs and the majority of holders?
Sure they could change the code to anything they liked - but in reality, it is only relevant if the whole community agrees and updates to this new version. If not, for all major changes (ie. adjusting the supply limit) all you would do is create a fork between the people using the older Bitcoin Core and the newer one.
Most of the big changes would cause a price collapse (I can't think of a major change that would be agreed upon which would cause a price increase) - which would inspire the mass of Bitcoin users to reject a new update. On that point I do agree - most are motivated by financial gain rather than coin itself, but luckily so far these are fairly aligned.
It would go on with new devs - maybe worse off but not dead. Reminds me of the Truecrypt project that packed up and instead got taken up by a number of different groups of devs.