It isn't a bad thing to make predictions, but the likelihood of success is small. Beware lists of successful predictions - that's like saying "how amazing! I flipped coins ten times, and all came up heads" after having chosen ten particular coin flips.
The value of thought exercises about - for example - friendly AI - is not that you'll be right on the mark; this rarely happens. The value is that you'll gain a bit of knowledge, as will thousands or millions of others via other predictions and experiments, and those many bits of knowledge will combine in interesting ways, some of them fruitful ten or twenty years in the future. You cannot test hypotheses which have not even been proposed.