It's okay. Sega didn't promote any of them, so Platinum can make new IPs that will be instantly just as well known as their old ones.

I actually think with Bayonetta they did a pretty good job. I forget what it was (avatar maybe?) but I remember being at the cinema and seeing an ad for Bayonetta right after one for Mass Effect 2. 

Madworld they did meh. I remember seeing a few net ads but nothing on tv etc. Vanquish I don't remember seeing anything at all and they pushed it out at one of the busiest times of the year. 

Platinum can certainly make new ips. Heck they could make a million brillaint new ips before Sega managed one. Doesn't change the fact it will be sad to not see any more of the cool characters and worlds they already created.