I don't like it to be honest. You have solid keepers, and I think Seguin is going to take 3+ years to put out any points that are even remotely fantasy relevant. Horton is "on the verge" every year... And every year could be that year. Cammy is also solid if he can ever stay healthy.
Purcell is garbage in a "Keep 7" league, and a 3rd-4th round pick will get you a decent player most likely... But I don't think it makes up for the loss of Horton + Cammy.
And I'll go out and say that Ennis, who's already on your team, will be better than Seguin for the next couple years... And if Ennis isn't a keeper now, does it make sense trading 2 potential keepers for a guy of similar value to Ennis?