My advice is to go for it now. If you get the 64 you will have all you need. If the iPad2 has something you can't live without, eBay will help you take care of your old one. I don't believe in waiting for something you aren't sure of.
I wonder why a 3rd party doesn't make a USB to attach to the iPad?
Why look for a third party replacement?
I'm getting mine for Christmas, so the only waiting I'm doing is 9 more days.
it's all good - mostly
You can spend the rest of your life waiting for better technology just around the corner and never buying anything!
New iPad wifi + 3G 64GB
Paired with Macbook Pro
Backed up to iCloud
I'd say buy now. Even if you only get four months usage from it I believe you will consider it money well spent.
Remember it will work just as well when the new iPad comes out as it does now.
I suspect that there won't be radical changes in the next upgrade, rather a refinement of the current model to keep it ahead of the competition and real changes will await iPad3.