The silly thing is that now that a number of people have offered their unsolicited opinions on something which may or may not happen, I feel the need to offer my differing opinion. I am aware that it is equally unsolicited.
As a user, I am not a big fan of subscription models - I have til now accepted them only when the price of the subscription over 3-5 years is close to what I would otherwise have paid for upgrades during that time. I used to believe that updates (to eliminate bugs and holes) should come free, whilst new functions can be charged for. The fact of the matter is, though, that for most material things in life, that logic does not hold true, certainly not over extended periods of time. I have worked with an unreasonable amount of software which has had bugs which were never rectified. I drove a BMW which had software flaws which were never corrected and - in the end - solved by the company degrading the available options in the software. So I’ve had to adapt to that reality (and I no longer drive a BMW 
).
I still balk at paying a subscription for any software which I don’t use on a regular basis; that software must offer me some noticeable value. As an example: I pay subscription fees to Adobe to use Acrobat Pro DC. Whilst I neither like the software, nor feel Adobe do enough to earn that fee (where’s the roadmap for the ARM version?) it saves me time and energy - because (once I’ve found a function) it just works. All the time. I tried numerous other PDF editors, and none came close and most instead failed at simple things like rearranging text or other components of the PDF.
Where does that leave me and DT? I happily paid for the upgrade to DT3 - and would “happily” pay a yearly fee to use it. It is a piece of software which has literally changed my life. Replacing it would cost me an enormous effort. I feel the team have done a brilliant job and are and remain extremely responsive both in the forum and in their work on the software. They are limited by the size of the team they have; but again, I have worked with software which is more expensive by orders of magnitude, but in which the simplest of user feedback cannot be or is not ever implemented. DTTG is free [Edit: my mistake] DTTG comes in at the combined price of 217 g of Swiss Emmentaler, 267 g of Gruyere, 228 g of Appenzeller cheese and one baguette with a small number of functions offered for a one-time fee which would not buy me lunch at the restaurant around the corner. Whilst I often wish it were more powerful, it is a perfectly good companion app - I wouldn’t be using it as a standalone app. Now, I’d pay a subscription fee to use DTTG too; I would consider the cost in the context of combined costing - I’m surprised DEVONtech can make a living from the software they sell at the price they sell it for, and would prefer for them to charge more than to go out of business. @eboehnisch when you drive a Lamborghini and start to entertain guests in your country mansion, let me know, and I might rethink.
As for the last update to DTTG being months ago - well, yes - I’m happy to accept DT were working on releasing DT3, perfecting it, getting it ready for Apple Silicon and Big Sur and probably pissing about with the same pandemic as the rest of us. Would I prefer perfection? Yeah sure, who wouldn’t - I’d really really like smart groups in DTTG. And I’m sure that if that is technically possible, I’ll get them one day. In the meantime - again - I don’t feel wronged by DEVONtech - a company known to respond to users on this forum every single day of the week - I’m not getting the impression anybody is sitting around twiddling their thumbs and going “yeah, come on, let’s see if we can get rich faster doing less”.
In the end, for DEVONtech and the handful of people who are that company the question must boil down to “what’s the return on invest?” And at the moment, I personally can’t imagine DTTG being balanced as far as that goes. A subscription model will lose DT some customers - but not much revenue.
So anyway, that’s my opinion (and I’m not representing DT; I’m just a random user who is honestly happy to have found this piece of software). And I’m aware that my own fortunes are such that I can afford to pay for what I use, and that not everybody is so lucky. My dealings with DT so far leave me with a warm cozy feeling that my data is safe in DT - I couldn’t say the same for some of the other products mentioned by others in this thread. I really need things to stay that way - free software is not sustainable in the long run - if you’re not paying, you’ve got to ask what the company is living off of.
For those who read all that: welcome to the end.