Nexus 4 or wait?

Hey everyone!

Like everybody here I heard that the Nexus 5/4 2013 is coming soon and I don´t really know if I should wait for the 5/4 2013 or buy the Nexus 4. I have to say that I don´t really care about gaming-performance because I do not have the time to play more than some minigames. Also I´m not someone who cares a lot about processor performance. For me the phone has to have a good user and software experience. From the pictures that have been leaked from the new Nexus I also don´t really like that plastic backcover but I like the back from the Nexus 4. So now I would appreciate if you could help me.

-Will the user experience be better on the new Nexus?

-What do you think about the plastic back?

-How long could I use the Nexus 4 before it gets slow?

-And your overall opinion about the new Nexus 5/4 2013

Thanks a lot!