no.
deepin is based in ubuntu
yoou have to reinstall the entire sytem,  if you want deepin 2015

This doesn't make any sense.

Exactly to be based on ubuntu, it SHOULD BE possible to a rolling release distro... In ubuntu you can do: apt-get dist-upgrade.
It will not be possible, ONLY (and ONLY-IF) developers don't allow it. So, if this is the case, I will regret of change my Ubuntu Gnome to Deepin....

No, deepin is not a rolling release; neither is Ubuntu. A rolling release has continual updates, not versions. Arch is a rolling release Linux. Long term support (LTS) versions provide continuing new updates for 3-5 years. Standard releases provide new updates until the next version. You can update any release after installation, but there may not be any NEW updates after a particular date. Relax ... there are updates for deepin. I hope this clears up any confusion.

But Deepin 2015 will be a different story. because it based on Debian.

Very true, ambiya, and Debian uses a hybrid approach consisting of three levels: stable, testing, and unstable. Stable stays pretty much as is to be consistently reliable under all circumstances. Testing is like a rolling release until the bugs are worked out and it becomes the new stable. Unstable is the developers' playground until it's alpha/beta level and replaces the previous testing, which then becomes stable. I'm not sure exactly what initiates transformations, but I suspect they occur when there is no impedance at any level. Debian stable has a reputation for being boring and good for business use. Testing is more interesting and good for personal use, like a beta version or release candidate. Unstable is the bleeding edge appropriate for advanced users. Keep in mind that Debian is very traditional and vast in scope. There's a lot of repository apps to test. Debian is not particularly user-friendly like Ubuntu, but it's much less CLI-oriented than Arch. If you want to try an inviting and small Debian-based OS, I would recommend antiX-15 or its cousin MX-14.