According to the theory they should still be on hold. Deleting "in trial" and other "on hold" keywords "frees" space for your other on hold keywords to run.
Robsp is essentially correct on both counts, although there is one nuance of the second point that I'd like to clarify:
Deleting 'in trial' keywords will immediately open up space for 'on hold' keywords, but the 'on hold' keywords do not move to 'in trial' randomly. Rather, it is the 'on hold' keywords that are predicted be have the best CTR that will then move to 'in trial'.
Also, deleting 'on hold' keywords will not actually open up space for more 'in trial' keywords.
What it does do, though, is reshuffle the order of the keywords that are in 'on hold'. So, bottom line, the system is continually ordering the 'on hold' keywords in rank order, which means that deleting keywords and/or adding new keywords that go to 'on hold' will cause the rank order to reshuffle.)
And if you delete 'on hold' keywords that are not really that important to you, then it will give the more important ones a better chance of moving to 'in trial' soon.
Hope that made sense. If not, I'll try again. ;)
AWA
One more question though. When you say 'more space' in the account, is this measured by the Ad Group or the whole account?
There really needs to be more clarification of this sort of thing in the AdWords FAQs. I'm sure this would cut down on the time you need to spend on support.