There's several reasons why this process takes so long, and why the products we've seen coming from the new Google-owned Motorola are essentially the same as they've always been - including non-vanilla Android. First, a hardware company like Motorola has a product pipeline that you can't just kill. Motorola's sales may not have been doing well, but declining sales is still better than no sales at all. Especially in the mobile industry, a product has to comply with boatloads of standards, laws, and regulations - and that requires lots of testing by both the manufacturer itself, as well as agencies and institutions all over the world. And remember - every country has its own rules.
This means that even if Google started designing Motorola phones right away after acquiring Motorola, these phones would simply not be ready now. So, instead, we're looking at the same old Motorola stuff the public had already grown tired of - including Motoblur.
However, the chances that Google started designing phones right away are slim. Motorola is a large company, and so is Google - the process of integrating the two isn't easy. I obviously have zero experience with something like that, but common sense can go a long way here. Common sense also states that it's probably a good idea to finish this integration process first, before starting to work on completely new products.
During the Google earnings call, CFO Patrick Pichette stated just that:
Remember that we inherited an entire product pipeline where hardware business cycles are typically 12 to 18 months.
I'm actually incredibly curious to see where Google will take Motorola. If my Nexus 7 - built by Asus, but Google has its hand in it - is anything to go by as to what to expect from Google's own hardware division, we'll be in for some great stuff. I don't want Samsung to remain as domineering as it is now, so hopefully, Google's Motorola can do something about that.