Here is Extension for 4E ruleset that gets you 90% of way to D&D Next (5E)

[JamesManhattan]

I made edits at home and tested it, it should work now.

[Ryankotu]

Hi, When I use this extension, my players are automatically receiving their proficiency bonus to EVERYTHING. Armor class, all skills, etc. Do I have to correct this manually every time they increase their bonus by entering a negative modifier, or have I done something wrong?

[JamesManhattan]

You can't type in Level in the level field on the character sheet, because 4E adds half level to every number in the game like you are describing. That's my guess as to what's happening.

Put their Level as 1 in the field on the first page of the character sheet. To keep track of their actual level I type it in right after their class. Like this: Fighter 3

Put in their proficiency bonus manually on the skills tab, to each skill it applies to, and then manually on the combat tab next to melee and ranged. I put them in as Misc modifiers.

[Ryankotu]

Perfect, thanks. I'm not very familiar with 4e.