I resisted getting an iPhone for ages. Couldn't see the value in getting the early versions. More I noticed people using them and I took a bit of interest in what they could do, I started looking into one myself. Now I have one, I don't think I'll have anything else.
Don't plan on getting an iPad. Yet
Regarding how soon they're releasing a new version - Canon (and I assume Nikon) release a new DSLR camera in each series every 18 months or so, and they've been around much longer than the iPad.