There are many things the author didn't think about. With Segregated Witness, the signatures don't need to be part of the 1MB block. Also for multi-sig we will be using aggregatable Schnorr signatures, so multi-sig won't take that much space. Still, the cost of an on-blockchain transaction will probably go up to $1000-10000 in current US dollars, so I believe even having an on-chain transaction will get too expensive for most people. For the short term lightning should be a relief though until the community can come up with the next scaling solutions (after implementing Mimblewimble as well)