In 5 years time they've still got to find £350m and unless the shares appreciate significantly they can't do this again.
Are we talking
1) Glazers sell up completely
2) Fire sale on players
3) The team have got to maintain there position in league, CL and be "sucessful" in eyes of the fans and punters alike.
4) Increased revenue streams through sponsorship, naming rights to stadia and the like over next five years to pay the debt down. You are talking 70m each and every year from profits to do that, won't leave much scope for squad improvements which they will need to do without the Wizzard. This will be driven very much by 3) above.