I respect The Sonic Stadium and know Hogfather through the merch forum there, he's a nice guy, but maaaan are they so way off base with their speculations there.
Let's look at the facts: SEGA of America has not been at any events or trade shows outside of Momocon (which was itself a small affair and almost exclusively Hatsune Miku and Japanese games focused). SEGA, not the developer, is in charge of promoting and previewing the game. It's been pretty clear that for a better part of the year, moving and hiring new staff has been priority over promoting games. Fire & Ice is not alone, just about every game slated this year has had little more than an announcement video and a few social network posts.
Fire & Ice was due to release within the next month, so the game would have had to have been finalized some time back. It is entirely likely that Sanzaru shifted work to other projects because they were done with the game. Shattered Crystal was a rush job, Fire & Ice reused a lot of assets and as such was also a quick project. Why is it a problem that Sanzaru has not been working on the game for the past few months when now is the period of time for a Holiday 2015 game to be out of their hands and in SEGA's?
Let's also not forget that people do not always update their LinkedIn (it's not Facebook, people) and listing specific games is not always done due to fear of titles leaking before being announced.
As far as the concern that Fire & Ice was made with a small team, how big a team is really needed for a 3DS sequel that reuses a game engine and other assets?
Here is my proposed timeline of events:
• Late 2014 Shattered Crystal releases, is enough of a success to warrant a sequel ("success" meaning it made more money than it took to develop).
• Late/Early 2015 - SEGA green lights a sequel and Sanzaru gets to work.
• Early 2015 - SEGA announces layoffs, restructuring, and the big move from San Fran to LA. Stephen Frost is laid off.
• Early-mid - 2015 Development continues on Fire & Ice.
• Mid 2015 - Aaron Webber and other new staff are hired and the move is completed.
• Mid 2015 - Sonic Boom Fire & Ice is announced to release late 2015.
• Mid-late 2015 - Fire & Ice is completed, Sanzaru shifts staff to other projects.
• Mid-late 2015 - SEGA Japan urges all regions to focus on quality, Aaron Webber (known for playing a part in Sonic 4 Episode 1's delay) and other staff agree that Fire & Ice needs more time. Sanzaru likely also pushed for more time.
• September 2015 - Fire & Ice delay is announced, behind the scenes dealings take place - DEVELOPMENT CANNOT SIMPLY START BACK UP. This is a business, money needs to be allocated and contracts need to be signed.
• September 2015 - Sanzaru posts to Facebook: "Happy to see Sega investing the time and money to add in the features that we feel will make the best Sonic Boom game to release alongside the popular Cartoon Network series."
• October 2015+ - Sanzaru resumes development once timetable and additional budget is sorted, all the thing Sonic Stadium worried about never were an issue.
• Early 2016 - game releases.