What are you comparing it to? The N900? Then I guess it's relatively fast and smooth.
The level of freeze, frame drops, general stutter and lag really hasn't been a thing on mid-range and above Android devices (carrier bloatware notwithstanding), iphone or BB10 for a while ... though with the latter there was occasional stutter on earlier versions. The most bizarre thing I find about these people claiming that Sailfish on the Jolla is so fast and smooth, is that they usually also argue that more powerful hardware in the near future is unneeded and would barely offer any benefit. Do they even believe this themselves? Sailfish has 'proper' multitasking, so if you're going to make real use of that or be a power user, you're definitely going to benefit greatly from better hardware ... add Alien Dalvik in on top of this, and an almost bottom of the range Qualcomm SoC and 1GB of RAM is perhaps not all that you could ever want.
I don't believe you for a second that your device is "always fast and smooth", unless you're one of the people that swear blind they can see no difference between 30hz and 120hz and never notice frame drops (which are constant on sailfish).
There is a very big middle ground between IP certification and the environmental sealing that the existing TOH offers. It should be improved on a new device.
Aesthetically and ergonomically the existing Jolla is a mess. It's a clunky brick with huge bezels and an inexplicably gigantic bottom bezel when the device has no hard or softkeys. Beautiful ... not sure you'll find too many takers outside these forums for that assessment.
I think it's fairly obvious what I'm talking about with regard to production and design considerations that an unchanged TOH for the next phone would dictate.
I think we can consider Jolla a dead duck if their new phone isn't on the market by this time next year. I'm pretty sure your confident assertation that it'll be at least a year or longer is not compatible with plans they may have.