But, he did explicity ask how it could be accomplished TODAY (I presume that indicates he is aware that this will be a non-issue when the new .iso is realeased).
I would suggest:
1) Installed from most current .iso (2009.2 as of this writing).
2) Setup YouCanToo's frozen repo, switch to it, and perform a full upgrade.
3) Switch to another ("unfrozen, but frozen for 2010?") repo, and perform another full upgrade.
4) Change the repo's setting, replacing "kde" with "kde4"
5) Perform another full update (need to select "task-kde4"?)
N.B., this is off the top of my head an UNTESTED !!! Mea culpa!!!
...perhaps doing this in a VM as a test run may be prudent (although I can't do that at the moment)...
...just thinking...you could start with the 2009.4 LXDE (slightly newer, smaller upgrade path?), maybe?