I don't think there is anyway the prices would come down that much. Because there is no real reason for them to come down.
Regarding the Mini-Tablet. I believe that has already been done. About 2 years ago actually. Project Origami by Microsoft which was revealed as the UMPC(Ultra Mobile PC).
Screencast of the Project Origami website from 2006
http://www.youtube.com/watch?v=t9JNgaRxMtU
The UMPC(Mini-Tablet) is also regarded as one of Microsoft's greatest failures. Because at the time of release they lacked a market, had out dated parts, and were way over priced.
The real problem of the UMPC was that Microsoft just ported their OS (XP originally) directly to the device. Hardware wise it was brilliant, but the operation system was way to lack luster.
Their are Linux devices as well such as the Nokia N800. Which is literally an Internet Tablet.
Then again the Intel Atom was just released and there have been a ton of Ultra Mobile lifestyle gadgets hitting the market.
However, if their is any company who can make a UMPC successful it would be Apple. I don't know though, on one hand it is a great way take market share. Then again it was a massive failure. It is definitely a very risky idea.
It would be more realistic for their to be revisions in the MacBook and MacBook Pro. I would love their to be a market for UMPC style devices, but I really don't think we are at that point quiet yet.