Will unity stop clients?

So are we going to be unable to hack now do to the switch to unity when it gets switched?
just wondering

It'll be temporary

Firstly, try a quick search on the forums first next time. This question has been asked and answered more than once. To answer again, if there is code executing on your computer, it is fundamentally possible for you to edit it, albeit with more or less difficulty in some cases. I'm not sure what kinds of tools are available to hack Unity programs, but I'm guessing that immediately after the port is released it will be like a reset to the early days of hacking Flash. People will start by editing at the bytecode/machine code level until they find or make better tools to decompile into something close to source code.