The problem is: you have to assume "something", because otherwise you simply can't make any predictions. Either assume progress is linear (which seems to be the instinctive default most people use if they don't know much about a particular field) or assume it's non-linear. In case of the latter, you can choose between assuming exponential progress to apply or a step-wise, non-continuous kind of progress. It's a bad idea to not assume one of these to be the case if you want to make a prediction, because it's not possible to predict anything without that assumption.

I mean, you can of course refrain from making any predictions. But I have never met a single person who could resist the instinctive urge to extrapolate current developments into the future. It is as much a core part of being human to do this as it is to breathe air.