Macworld's Christopher Breen speculates that Mail, Stocks, Maps, Weather and Notes will be available for older iPod touch models as part of the 2.0 update coming on July 11. The apps are no longer available via the January Software Upgrade through iTunes. (Try clicking the link on this page to see what happens: nada.)
If you recall, The Stevinator said during the WWDC keynote that the 2.0 update will be available to iPod touch users for $9.99: half the cost of the January Software Upgrade that brought those apps (officially) to the iPod touch.
This move is sure to perturb the users who already bought the apps, who could be nearly $30 in the hole for something that will cost others (me, for example) a slim Hamilton.
I can think of a worse situation for iPod touch owners: Apple offering the apps individually via the app store, at some undetermined cost for each one. I have no reason at all to believe that will happen, and I really hope that it won't.
Update: Speculation alert! Christopher Breen (himself!) said in comments that his source for this information is a little shakier than he thought. He's updated the original article, and this post's been placed in the Rumors category. So add a few more grains o' salt to this one.