(How) can I evaluate, whether a field has a future or not? I'm new here, so I hope my question fits in:

I am trying to decide where I should do my master thesis, and since I am considering an academic career, this could be a fist step towards the field I will finally end up working.
With my education up to now, there are two fields, where I would fit in, and that's where my problem begins: 

The one field I find far more interesting seems to be kind of "Out of fashion" (or at a dead end?) with lots of publications from the 80ies and 90ies, and nothing that looks to me like a big advance  since then. But of course that's just my un-informed impression, and I don't know how far I can trust that... I tried to ask a professor working in the field, whether he thinks, there will be advances in the future, but I formulated my question very carefully, since I didn't want it to sound like "is your area of research dead?", so I am not sure, if he did understand, what I want to ask and shrugged it off, if he was personally offended, or if he didn't understand the question at all.*

Dear people with experience in the academic world, how could I find out, whether a field has a future or not?

Is it presumptious to make these considerations as a student?

If my University largely reduces the funding of research projects on that field, is it a sign that I should forget about it?

If you were a professor/postdoc etc. in a field that has already seen its best days, would you tell a prospective student?

Does it even happen, that a field "runs down" ? And if, why? What does it look like for the people still working there? 

How was it for you, how did you weigh the interestingness of the field against future job prospects, when deciding for a specialization?

If that makes a difference: Both fields I could choose are in the area of Biomedical Engineering/ Biochemistry - I do not want to name the field, because I don't want to be "the idiot that said xy was dead", and I don't want to offend anyone working on it. Also answers to my questions would be more helpful for me than opinions on the specific field. 

Thanks a lot &amp; sorry for the long wall-of-text-ish question !
- NewBie

*You get an idea how good I am with that kind of thing. Please help me.
You have started well by looking for recently published papers. If there are none, it could mean your field is very small and you will find it hard to get future jobs and funding or that you are not searching in the best places. Maybe you could ask the professor if he can recommend any more recent papers for you to read to "understand the current progress and see if it matches what you want to do" or something like that. If he says nothing has been published more recently you can ask why. 

You could also ask about or search for conferences or meetings. It may be a field that does not produce lots of papers but still has a large community of active researchers, so would not seem "dead".

If your University has cut funding in that area it will definitely be harder to get a PhD there after your Masters in the same topic.

But it is an important point that the topic of your Masters doesn't have to relate directly to your PhD or future career. It's a good chance to try out an area you might be interested and see if it suits you, and in any topic you will learn research skills that can be put to good use in a PhD. I know many people who started PhDs in subjects they had never studied before, but you must show that you can learn new things quickly and have all the other "soft skills" of research: writing and presenting, finding and citing good sources, data analysis, critical thinking, using any relevant software or machinery... these will depend on your subject area.

You would probably produce much better work in your Masters project by taking the option you are most interested in. You can then have time to get familiar with the academic community, let your supervisor know you are thinking about the future and want to find out what it is like, and if it is a dead end you can take a different subject for your PhD so long as you are not missing any core skills.

Good luck!