Quote - If the deal after a month is that they will simply give Complete owners a voucher for $400 towards the cost of a separate full copy of Infinite, then that means the customer is left with a copy of Complete for which they have no use and basically would then own TWO copies of Vue.

While that may be true for you, it's not necessarily true of others. For instance, a small graphics studio.

Quote - That could be seen as generous on the part of e-on but also a sizeable waste of money for the Customer. Why they can't just charge an extra $350 and then cancel the Complete licence is beyond me.

Probably for the same reason Adobe doesn't allow upgrades from Elements to Photoshop. IOW, they're trying to build a distinction between the Pro line and the Artists line. I'm not saying it's correct, but I believe that is their reasoning.