Next version

NetHack 3.5.0 is the mythical next version of NetHack, also known as Net Hackem Forever. It has not been released yet, and there is no information available to suggest when it will be, other than "When it's ready."

Version number
Possibilities are 3.4.4, 3.5.0, 4.0.0, or something else.

3.4.4 seems unlikely, unless a major security hole is discovered, in which case it may be released with only the bugfixes marked "fixed" (lowercase f) on the NetHack bugs page.

An increase in major version number to 4.0.0 also seems unlikely, as the last major bump was 17 years ago, since when many, many major features have been added. Such an increase doesn't fit in with the DevTeam's observed pattern of extremely conservative behaviour.

"Something else" is a possibility, but again would be uncharacteristic.

This leaves 3.5.0 as the likely next version number.

New features
Only two things are certain: it will not be savefile compatible, and it will implement a #tip command.

News of this last feature was leaked in July 2003 by Pat Rankin in this RGRN post:

This capability has already been implemented for NetHack version $(NEXT), for some value of $(NEXT) greater than 3.4.2. (At present the command is named #tip rather #dump, but that could conceivably change if your patch actually makes an impact. It has handling for containers on the floor as well as in inventory, for cursed bags of holding, bags of tricks, altars, levitation, and for one or two other things you'll probably overlook. ;-)

Its primary purpose is to provide a means of getting things out of containers when your hands are stuck to weapons and/or shield, but it will work at any time unless you're too heavily encumbered.

Rumors that Pat has since been executed by the other DevTeam members for this rare breach of secrecy are unconfirmed.