Perhaps. Some existing code will not work without modification and recompilation, unless MetaQuotes unwind some of the changes they are making such as new locations for things like FileOpen().
Most of my indicators do not work in the Beta.
In addition to the different location the lazy fetching of libraries is longer working. I cannot embed libraries into indicators any longer.
I think that's just a bug, which will presumably be fixed, rather than something which is definitely changing like the location for FileOpen. DLL imports also don't seem to work yet, either from <mt4>\experts\files or from %appdata%\metaquotes\terminal\<xxxx>\mql4\libraries (but they do work if the DLL is in the mt4 root or in system32, so it's not the case that DLL imports are being abandoned).