The original Le Pan is not upgradeable to 4.0. In fact, Le Pan removed any fireware updates for the device from their website.
There is an on going thread here about 2.3 for the le pan. Don't know if they ever got the wrinkles out though.
You would be better served to buy one of the big names if you want continuing support. I recently bought an older acer model and it automatically updated to 4. Toshiba is a little slow. I'm still waiting for 4.0 for my Thrive. I think the other majors like Asus and Samsung offer good support and updates.