The story of gadgets/tech goes like this.
Buy it (or even order it online & wait a month) and it's already 'out of date'
The worst time to buy any gadget - if you're concerned about keeping up with the Jones' - is when a product is 6 months old, because in 6 months there will most likely be a new model. Hence, buying an iPad now is a good idea. Waiting till Xmas to buy one, not so much.
As soon as a company is ready to release a new product they're already - or have been - working on the next one. Thus far Apple has been on a roll establishing itself as the one to beat and therefore can almost dictate when they want to release products to the market & competitors. All you have to do is look at Samsung and the Galaxy tab 10.1 debacle of thinking they had a worthy tablet alternative, then releasing a new thinner version under the same name within 2 months! That's where you'd have to be 'worried' about snap-release new products (but remember, you can't buy either of those tablets yet!). Regardless, this power within the tech market place has shown that 10-12 months is the minimum 'shelf-life' of an Apple product - bar the G4 Cube. I could get into the economics of R&D vs. Product/Sales Life... but basically doing what Samsung did= bad. Selling a design for as long as po$$ible=good (just look at the refreshed MBP line/rumoured iMac line refresh- same outer shell, different internals).
The rumours stem from the speculation of just what iOS 5 will enable users to do.
Fact: details of the new iOS will be released to developers (and hence the world) at WWDC 6th of June.
Fact: nobody but those within Apple right now knows the details of iOS 5. Unless someone has broken ranks, it's all rumour.
Like any tech company Apple wants you to buy new products- it's how they earn a crust/Bentley. However, they also know to not burn their customer base by making products obsolete after 1 year. So iOS 5 may be revolutionary and be more "magical" than ever, however I'd put money on it working without issue on the iPad 2, work on the iPad but maybe with the loss of some small features if any (might just be slower) and of course work on the yet-to-be-conceptualised iPad 3.
As mentioned, there might be a revamped iPod Touch/mini iPad 2.5 type device- a in-between device and/or smaller tablet. However, that's all just rumour.