Why would the iPad 'need' 8GB of RAM when it's running specific optimised apps? Doesn't make sense, these aren't PCs that require a big overhead to run, they're a completely different thing. I think Samsung puts large RAM in their phones because A) they don't control the OS, so need the overhead. And B) I think it's probably cheaper for them to produce certain chips, and claim "WOW, look! So much RAM!".
Also if they do come out with an upgraded iPad, why does everyone assume that people who just brought one will need to fork out money to buy the next? It's not for them, the new iPad is for new users, if they don't upgrade them then the market stagnates. People who just brought one don't need a marginal speed boost, of course some do, but Apple expects those to upgrade on a 2-3 year basis.