If there are updates, someone will post them. If you see an update out there that isn't posted here, you can post it here. If you want to know if there are any updates and you don't see one here, you need to go research elsewhere yourself. If you find something relevant and worthwhile while doing so, share. If not, you have your answer.
Anyway, do not bump threads asking for updates. It wastes everyone's time.
Eh there's been updates, would require a thread reset at this point though.
Project Horizon for all intents and purposes has been either shelved, outright cancelled, and/or had the contract move elsewhere. There's been no movement to suggest it's even still being considered, let alone happening.
Alton Towers is getting an entirely different coaster in Cbeebies Land for 2026. Here is progress on the ground;
The park publicly submitted the initial plans in December, from which a planned maintenance building was cut and the footprint/queue layout shifted to save the trees. To accommodate the coaster they had to briefly close their Treetop Adventure aerial track for a reroute and also retired Postman Pat's car ride in June, the site of which is as seen above. Here's the full planning page. It's essentially a giant oval, do not be fooled by the scale.
Based on the lift hill, early connected footer shapes, and other ongoing contracts with Merlin, the coaster is heavily favored to be from Zierer. A Bluey theme is rumored but not rooted in evidence.
So yeah, this isn't the big indoor coaster but arguably something that Towers really needed. A high capacity junior coaster with a minimal layout to appeal to the ages and a very large train (everything their current kiddy coaster isn't!).
To my understanding the original plan would've included a straightaway from the lift hill rather than an immediate turn into a descent. New one may be longer but it seems to mostly be cutting down the footprint a bit by condensing the track length rather than purely lengthening it.
Descending right turn off the lift hill that goes into a slightly banked hill, drops under brake run and does a figure eight, before hopping over the previously mentioned track and into the brake run.
I'm not the best at describing things, I'll make a mockup later.