will this kill the current modmakers or
No, it might even make modding easier and bigger!
Sure they will have to learn C++, but once they get rolling, mods will not just be much faster and have less of a performance impact on the game, but they will be able to do even more robust things.
Considering there will also be an official mod framework, that means mods will not break that often in updates, sure they will be slightly broken, but now we will be able to use older mods to an extent in newer versions as long as core parts of the mod framework is not touched.
Lets just recap on the current versions of Minecraft and what they actually are :
Minecraft Desktop Version (Windows, Linux, OSX)= Java 32/64bit
Minecraft Pocket Edition (Mobile) = C++
Minecraft Console Edition (Xbox, PS, WiiU) = C# or Visual Basic
Minecraft ARM Edition (Raspberry Pi, PE Variant) = C++
Minecraft Windows 10 Edition (Not PE, some code from PE was recycled in the Beta) = C++
Basically there is 3 versions of Minecraft, probably a fourth but I have yet to find another, the Java Version is probably the worst performing one, Minecraft PE running very smooth on mobile devices is mainly due to the fact its Codded from the ground up in C++.
It is possible that there may be a Minecraft 3DS Edition (New 3DS Exclusive), that will most likely be a branch off of Pocket Edition, and its definitely possible seeing as how well the C++ version runs.
Basically once the C++ Version is completed and has all the features of the Desktop version, Mojang will probably start letting people switch version for free like Microsoft is giving everybody the Windows 10 Edition of Minecraft free if they own the normal one, from my understandings it will not be too hard to port to other OS so the Linux and OSX versions would probably be released shortly.
By then they would have no reason to continue supporting the Java Version, the only people that will stay there are modders that refuse to switch from Java to C++.
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