You never can tell what’ll happen in the future.
Is this correct? It may be a proverb or something, but i would translate 先の事など as “the previous things and similar”, so I would interpret it as “you cannot predict things like these”.
Very interesting question! Yes, the original Japanese sentence is actually correct and sounds natural.
先（さき）can mean either “future” or “previous”. It depends, but the Japanese sentence can NOT be interpreted as “previous things”. You need to pay attention to the verb 予想する = predict. You cannot use 予想する when you refer to past events or facts. 予想する consists of two words: 予め means “beforehand” and 想像する is “to imagine”. If you want to throw a new theory on a past unsolved mistery, you should use 想像する（そうぞうする）or 仮定する（かていする = assume）instead of 予想する. Therefore, 先のこと in this sentence doesn’t mean “previous things”.
Please keep in mind that the primary meaning of 先 is “ahead”. I give you example sentences to illustrate the difference between “future” and “previous” cases.
- この先の角を曲がれば、銀行がありますよ。（このさきのかどをまがれば、ぎんこうが…）= Turn the next corner, and you’ll find the bank.
- 台風や地震など、先々のことに備えて政府は災害対策を打つべきだ。（たいふうやじしんなど、さきざきのことにそなえてせいふはさいがいたいさくをうつべきだ）= The government should proactively implement counteractions against possible disasters such as typhoons and earthquakes.
先代の遺志を受け継いで、私はこの店の良き伝統を守っていきます。（せんだいのいしをうけついで、わたしはこのみせのよきでんとうをまもっていきます）= To abide by the wishes of the deceased predecessor, I shall keep the great tradition of this shop.
後にも先にも、そんなことを聞いたことがない。（あとにもさきにも、そんなことをきいたことがない）= I have never heard of it, and I will never ever in the future too.
先立って必要なのは、金と人脈だ。（さきだってひつようなのは、かねとじんみゃくだ）= What I need the most (to do something new) is money and personal network.
Example #1 & #2 with 先 mean “future” and also “ahead”. The next corner in example #1 is lying “ahead” of you, and you will see it in the future. Possible disasters in example #2 haven’t happened yet, but you will encounter them so as you will find the bank in example #2.
Example #3 & #4 with 先 mean “previous” and also “ahead”. The predecessor of the speaker assumed the leadership position “prior to” the speaker. So, the predecessor was “ahead” of the speaker. 後にも先にも in example #4 is a common set phrase. 先 in example #4 refers to previous cases whereas 後 means the future. You are supposed to follow the same trace as previous customs and leading cases. Therefore, 先 means “ahead” of you.
Example #5 with 先 means “beforehand”. 先立つ literally means “something stands in front of you” (= ahead of you). Whatever endeavor you want to pursue, you need something to achieve it.
Thank you for the clear answer! I have added your examples to my personal collection, that should help getting familiar with the various meanings 先 can have!