Whatever people's thoughts on him, Alan Biggs is extremely well connected across the local teams (esp. Chesterfield and Utd) so it may be worth paying attention to what he eludes to. Personally, I've also heard from within the club that significant, additional investment is in place to come onboard if/when promotion to the Champ is gained (although admittedly, that was > 6 months ago).
In terms of what that actually means, nobody should expect £multi-million signings and more like further building on CW has already created to enable Utd to be competitive. I'd be surprised should there'd be any bigger signings than the level of players such as Webster, Gregory, EEL i.e. £750k-£1m and most will be considerably lower than that.
That said, it must be remembered that transfer fees are no the be all and end all in recruitment. A number of very good players will become free agents in June and I'm sure CW, Mitch etc. will already have well developed recruitment plans, whichever division the club is in next season. As well as increased revenue from Sky, ticket receipts and commercial activity, it must also be acknowledged that outgoings will increased in terms of salaries, policing, ground development etc. and it would be still extremely likely that Utd would generate an operating loss, which of course would need to be covered.