@msdev

I view it this way, since you actually would have paid 75 x 4 = $300 for those 4 months in any case (if in Canada) , you are actually getting out of contract in $100 by paying $400. I Think you got an opportunity to break it out wiht Rogers , if you want it that way. When you return you will have new and perhaps cheaper options, new handset.
Though as dude.. said you must also check any penalty arising due to discounted handset.

one negative side is you lose your number which apart from people you must have given to your employer, banks, insurance companies etc. But thats part of number change activity and will have major impact.