yea, should be around this week mate,
just checked the May scan, it even said April 25

https://www.youtube.com/watch?v=e88QHgKEXEQ
I have no fucking clue how the Gashat's supposed to go in, short jingle though I assume

Might it latch on top of Maximum Mighty (I haven't actually got it physically so I don't know if there's room)?

I actually have the Gashat myself and I think that it's gonna work like this.

Driver closed, pop in Maximum Mighty, latch on Hyper Muteki then open the driver and click in the Ex-Aid into the gashat and the button on Hyper Muteki (I'm assuming this is why the button Maximum Mighty has a giant A on it). Or another thing could be that once you press the button on Hyper Muteki the little black button gets pushed in and the gashat itself just latches onto the plastic.
Judging from the scans we saw I think the Hyper Muteki gashat itself folds open to cover the Gamer Driver screen.

The video forgot to show off this what I'm assuming is a re-activation button, if you press the button again a weird "activation" noise gets played and the gashat starts flashing colours, could also be a Critical attack.

The Muteki's jingle remind me to some of Beethoven musics....

Kamen Rider Ex-Aid Bike Action Gamer in Ganbarizing Game:

https://www.youtube.com/watch?v=IfMvTd4b2W8

just checked this
looks like we are gonna wait 1-4 days
http://www.cdjapan.co.jp/product/NEOBK-2031331

Just saw the new scans on twitter

Kiriya Revived but why he against Emu?:

https://scontent-sjc2-1.xx.fbcdn.net...10&oe=59A3B860

https://scontent.fhen1-1.fna.fbcdn.n...57&oe=599E3845

Ninja Rider:

https://scontent-sjc2-1.xx.fbcdn.net...8c&oe=599DEAD8

https://scontent.fhen1-1.fna.fbcdn.n...df&oe=59AC0512

More Ex-Aid vs Cronus:

https://scontent-sjc2-1.xx.fbcdn.net...a1&oe=59B15594

https://scontent.fhen1-1.fna.fbcdn.n...76&oe=59B856D4

Taddle Legacy:

https://scontent-sjc2-1.xx.fbcdn.net...71&oe=59B10D3B

^Cronus revived him:
https://scontent.fsgn2-2.fna.fbcdn.n...3e&oe=599FC4F5
Top left and middle bottom