As of right now the coin that's going obsolete is bitcoin because it's simply too hard to change, and this is a positive trait in itself but not if you are aiming for real everyday usage, which is where LTC with segwit and LN kicks in.
Litecoin with or without whatever implementations - it will not change anything in how people use it. It's nothing more than a coin that gets boosted from time to time by whatever entity with certain intentions, that obviously going to play out in their advantage. Bitcoin needs to scale, that's something we all can see (aside from noobs just ignoring everything and play happy user). But the main problem is that pools are playing hard to get, and thus knowingly hold Bitcoin back from growing further. In that regard, it may take a serious amount of time before we are going to see any sort of upgrade in blocksize. Direct result of that is that people will *temporarily* look for cheaper and faster (in terms of confirmations) alternatives.
Cryptos are useful in making certain payments like paying for a VPN. If nothing changes, we'll see $1 fees in BTC. Who is going to pay things like those type of subscriptions with BTC when you got LTC? get real. BTC will stay a hodlers coin as long as the necessary changes don't happen.
Litecoin is just one of the plenty of coins that people can choose from. If you ask the majority of the crypto nerds/enthusiasts what they will prefer when it comes to using certain altcoins as payment option, then it's either XMR, DASH or ETH.
What is the closest thing we have to a scalable BTC? LTC. Becuase they are the same, so you can easily port code, so BTC development isn't wasted in testnet and can be ported in a real ecosystem.
It doesn't really matter in this case since there are other coins that can function perfectly fine in terms of being a payment option, that also happens to be a cheap (compared to Bitcoin) option to use. As I said, Litecoin is just one of the plenty of coins that people can choose from. If it is up to the majority of the people, they will give the preference to one of the three afore mentioned coins, so no matter what changes Litecoin goes through, it's up to the end user to decide whether or not he will use it.