It's in ppa for precise. Either switch to precise when it goes stable April 26th or use the binary installer.
Wait for April 26th.
Use beta(but then you can't ask questions here...)
Use the binary installer for your architecture from here. The procedure is documented here which is the page you get when you click Offline installer on the previous.
"On Linux/Unix, you need to make the file executable in order to run it. You can either do this with your desktop's file manager or, at the command line, type:"
chmod u+x Qt_SDK_Lin64_offline_v1_2_en.run
You should now be able to execute the file as normal. You can do this from the command line by typing: