This, unfortunately, is happening now. NASDAQ is way down today, and the biggest bearish market movers are all in tech: Facebook and Alphabet and Apple. By itself this day wouldn’t and shouldn’t cause much concern, but the downward slope has continued since Trump won the election, so the concerning part is that the trend may continue for years. Bye-bye tech for the next half a decade. And since I am in technology, it especially concerns me.
It would probably we wise to diversify holdings into market segments other than technology. I recently purchased some stocks of a weapons manufacturer and it hasn’t been bad so far.