Is there a way to edit my personal maps within Google Maps or any other application? I remember that there was an application from Google to edit my personal maps. But it stopped working from Android 2.2 on and now it's even removed from the Market.

Are there any plans of integration that functionality directly into Google Maps or is there any other application out there where I can edit my maps?

Via the layers in Goole Maps I can view my personal maps, but I didn't figure out how to edit them.
Unfortunately I couldn't find My Google Maps Editor either.  I can't read Google's future and couldn't find any indication of such a feature but Google's My Tracks does allow you to upload a map to your maps but I'm pretty sure you'll actually have to run/walk/bike/move-in-some-way over the course you want to map.  

I also did a Google search for "my maps editor apk" and looks like you can still find the apk somewhere (I'll leave that to the you) but I can't say if it will work or not and you should always be careful downloading apps from unofficial sources.