Every company has a right of service, or the ability to remove a service... so Sony could turn around tomorrow and remove the WipEout HD servers if they so choose to... or limit the service, eg: servers online between certain timeframes...

I personally have never read through any of the fine print on the games, but it would seem that a game in SCEJ eyes will be supported for a minimum of 1 year... (assumption would be the same for SCEE, SCEA, etc...)

After that time, if the game community has moved on and no one is playing online, they will provide notice that the online part will be removed and it will be offline only from then... it's just a cost saving function, if no one is playing, then that server can be used for a newer game that everyone is playing...