with more than half a season left to be played, it won't be ... Milan won the scudetto last year thanks, to a big extent, to their winter mercato - MvB and Cassano. Similarly, Juve can fix their CB in the winter without that costing them a CL qualification or anything of the sort.
As for the CL, by then it would be only group games and it's a pretty straightforward one to deal with this year, as it seems. After that, Milan's ambitions in the CL will be determined by their winter mercato.