ACR always goes with whatever the current release of PSE is, so PSE10 would be able to handle ACR 7 unless PSE11 has been released in the mean time. Elements has usually been updated Septemberish so I’d expect ACR 7 to work with PSE10, still.
I guess we'll find out for sure only if they release ACR 7 as an install patch like ACR 6.7
if anyone is able to install ACR 6.7 RC into PSE10 - please let em know...
Adobe does not make release candidate versions of ACR for Elements. So Elements 10 users will have to wait for the final version 6.7 release. Sometime in May 2012, when Photoshop CS6 is released, ACR 7 will become available for Elements 10.
(I have no insider status at Adobe, but can count to 12 , months that is. )