We know that Nokia has 2 phones planned for release with WP8.1 (April time). I think they will still be branded as Nokia then.
I think once Nokia becomes part of Microsoft, we will still see a big range of colourful Lumia branded phones, but then I think Microsoft will also release a single Surface phone, which is more in line with their surface tablet designs. Since they will already be producing first party phones, there is no reason not to produce more. I think the Surface Phone will be released in October 2014, along with Surface 3. And it will be a phone that is updated yearly, like the iphone or nexus.