Or LN could be solution if we wanted it to became mainstream currency. Although LN is still very slow as far as adoption is concern.
LN isn't a solution to that. It's just one (currently very dominant) second layer, which we in the future will see compete with other second layers. I don't rule out to see a second layer gain more popularity at one point.
People often look at LN as being Bitcoin's path to scale, but you don't really scale anything aside from the second layer itself. Bitcoin's main-chain is still slow and expensive relatively speaking, that won't change any time soon.
SegWit on the other hand is an actual scaling implementation. It brought a 20-25% transaction throughput increase and some bug fixes. Better something than nothing at all I would say.