Honestly, I doubt the UF defense will be as good next year. Replacing Bostic will be harder than most gator fans will admit, and you don't just replace first round guys like Floyd and Elam like it's nothing.
That being said, UF's depth in the secondary is ridiculous. Corner and Safety are going to be fine, great even. The DL is going to be better as a whole, than last year. Powell is back, Fowler and Bullard had strong years as true freshmen and will give UF it's best pass rush up front since 2008 and 2009.
The middle of the DL isn't as talented with Floyd's departure, but Easley is going to have a big year, and the depth is better, overall. Orr and Jacobs are going to be pretty good, and Darrious Cummings is going to play right away. Bostwick and Brantley probably won't even get a chance to play this year unless they blow up in camp (both talented freshman) and that doesn't even tough on guys like Sherit, Ivey, and Cox who could all contribute this year. The DL depth is the best it's been in many years in Gainesville.
The only weak spot on the defensive roster (and weak is relative) is LB. Morrison missing games hurts, because there aren't a lot of players at MLB. Michael Taylor has been good for Florida for a few years now and will start at one position. Ball and Kitchens are two guys that have played a ton of minutes at Florida and can play a lot of positions at LB. Alex Anzalone and Daniel McMillan are two guys that will add depth right away. In fact, Mcmillan has been such an animal he may well get into the starting rotation.
Long story short, given the coaching and the returning talent, UF is going to be stout on D, just maybe not top in the SEC.
The losses hurt more on offense, where the OL isn't that good so losing two projected starters like Halapio and Garcia to potentially lengthy injuries is bad. However, we don't know right now if it is lengthy, and both are expected back as of now. Jones really hurts, as UF was going to rely on him, but UF has a lot of talented depth at RB positions. Taylor, Lane, Brown, and Trey Burton (UT fans should know this guy) will be able to carry the load will Jones rests up. Jones will probably be back by Miami though.
Driskel is the biggest issue. He must come back healthy. UF won't be very good without him.
I know, TL;DR, but just in case you actually cared since you started the thread.
Regardless, none of it really matters, as the UT game is week 4, and all these injuries should be cleared up by then. The injury situation will probably be completely different by UT week. Also, UF has a bye week before UT.