I have seen and used GPG for portable Thunderbird for awhile now via GPG_for_Thunderbird_Portable_1.4.11.paf.exe
Upon the GnuPG site they list GPG 2.0 being available and supporting OpenPGP (enigmail) but only as source code.
So I looked into Gpg4win which is free and open source which aim of Gpg4win is to keep a Windows installation package up-to-date including the crypto software GnuPG.
Therefore I made a new folder in the Thunderbird Portable directory Thunderbird>App>GPG2 and placed some of the files extracted from Gpg4win into this to update and use the latest version of GPG from within Thunderbird Portable.
From within Thunderbird Portable>OpenPGP>Preferences>Basic Settings I made sure the GPG was found in this new folder via the overide option.
The files I used from Gpg4win were
gpg2.exe
gpg2keys_curl.exe
gpg2keys_finger
gpgkeys_hkp.exe
gpg2keys_idap.exe
gpgv2.exe
iconv.dll
ibadns-1.dll
libassuan-0.dll
libgcrypt-11.dll
libgpg-error-0.dll and
zlib1.dll
I have tried it a few times and just testing it out now.
GPG itself supports both versions as official releases (1.4.x and 2.0.x) and does not make a Windows version of 2.0 available. We prefer to stick with the official 1.4.11 release, especially as 2.0 gains you nothing at all when GPG is used in conjunction with Enigmail.
Sometimes, the impossible can become possible, if you're awesome!