I'm not seeing how you get them cheaper than the current TSLA '18 $320 calls (say you can get those at $6). That means you spend $600 to be able to buy 100 TSLA shares at $320. If you bought a SCTY '19 $35 call (say you get it for $0.8, or $80 for 1 contract), that lets you buy 11 TSLA shares at ~$318, so you paid $80/11 = $7.27 for the right to buy 1 TSLA share.
Still a great discount, because of the arbitrage, the cheaper time value of the extra year for SCTY, and the fact that you can get it now, while TSLA is still on sale this week. But not cheaper than the comparable TSLA options for 2018.
As far as the options disappearing, I just don't know. The general consensus here seems to be that one contract for SCTY turns in to 1 special contract of TSLA, with a weird strike price (say $318.18) and an "options multiplier" of 11, instead of 100. I am not an expert, but I'm willing to risk it, because my limited research confirms this.
Edit: Agree that there is the additional disadvantage of them being thinly traded post merger. I'm thinking if TSLA is at $500 in mid 2018, the time value of anything this deep in the money is negligible, so you'd just exercise the options and sell the shares. Being special options with only 11 shares makes them way easier to exercise (it costs $3500, not $32,000).