I don't believe that a bullrun will bring back dead altcoins to life because investors have a lot of coins to choose in the crypto market today. If that dead altcoin have the potential to grow, many investors will buy it during its initial offering, and would survive in many market conditions. There are still many ICOs in the market even it is already overtaken by IEOs. They can still profitable and but they need to have a believable product and a proper timing to enter the market.
That right, this year or next year bull run will not have any impact on some coins like the way it was in the last altcoins run, which the reason is what has been stated in your comment. There are too many coins now with serious hype for investors to be digging dip into old coins that are dead and probably below the belly of coinmarketcap.
Imagine me as an investor going to market now to choose randomly on coin to invest in, the only thing I usually do when I get to CMC is to look at the top coins generally, and then go to alts session and also pick from the top coins, so how can investors get to see dead coin when their target would be top coins in the market.