Rumours about version 2.5 maybe as soon as Baku;
source; http://f1sokuho.mopita.com/pc/free/inde ... 60&tt=1170
Rough translation;
Honda decided against introducing a 'spec 3' with upgraded combustion chamber at Canada. Hasegawa wants to introduce as soon as possible but not making promises as to when.
Author speculates it's hard to think drastic improvements can be made in 2 weeks till Baku, so the author thinks its reasonable to think at the earliest Austria, if not Belgium.
Hasegawa is quoted saying "the ICE for Baku may not be entirely the same spec as Canada and will have some kind of new parts. Whether it'll be the step 3 or step 2.5, we don't know." ICE used at Canada was the engine used at Spain and Monaco, but some changes were made outside of FIA's seal.
Author speculates that if the Monaco engine was step 2, the engine at Canada could be called step 2.1 (and seems to think upgrades, if any, for Baku would be for increasing drivability and reliability, not power... which I think is logical). And the author thinks Baku engine may be any iteration between step 2.2 to step 2.9.
Author thinks another reason to bring even any small incremental upgrades to Baku is, although Honda hasn't had results showing that the step 3 upgrades are ready for GP, to lessen resentment from Zak Brown and to take full advantage of the abolishment of tokens.