The following general instructions may help convert an AI Classic app to an AI2 app:
AI to AI2 conversion
To convert AI Classic blocks to App Inventor 2 blocks, the advice in Scott's link might help...the link outlines some of the differences between AI Classic and AI2:
The AI2 free online eBook
http://www.appinventor.org/book2 ... the links are at the bottom of the Web page.will help you to learn to code with the AI2 blocks. If you understand AI blocks, the conversion will not be difficult; just time consuming.
Prior to 2013, you coded in App Inventor (now called App Inventor Classic). You can not directly convert AI Classic apps to AI2. AI Classic source code is stored in zip files; AI2 in aia files (which are actually zip format). The two source code files are totally incompatible.
To update the app from Classic to AI2 you can not use the apk. You have to manually convert the AI Classic blocks to AI2 blocks and recompile in AI2. When the conversion tool is released, it most probably will not perform miracles, users will have to fix things manually.
So developers, why are you procrastinating...start manually converting now and enjoy the benefits of AI2. The wait for the tool might be very long.