I'm a little skeptical Orlando would have hired Skiles if they thought doing so precluded them from keeping Harris, but maybe they would.
Again, though, unless Orlando has salary cap issues I'm not aware of, or has designs on major free agents (seems unlikely), I don't see the rationale for not matching on Harris, even if he's not in their plans.
Sign him and then trade him later this summer, if you have to. Unless you think it'll be difficult to trade him once he's signed to a large deal, it doesn't make sense to just let an asset walk for nothing.
Perhaps I'm overestimating what Harris's trade market would be like if he were signed to a 4 yr / 50 million dollar deal.
If signing him puts them well over the cap, then perhaps it starts to make sense. Because even if you trade him, you need to take back salary. This is where the decision to sign Willie Green, Ben Gordon, and Channing Frye last summer starts to seem very silly.