IMO ditching the electoral reform promise won't be that big a deal in 2019. It's not a bread and butter issue. It has been hard to explain in the past, a little inside baseball-ish. It won't lower taxes, reduce the deficit or put $$ in wallets.
Basically it made sense when the Libs were looking like third-placers. Now it's, "why fix it, we're in power, the system works!"
Personally I prefer it but I'm not crushed if it doesn't happen.
I feel the same way more or less. I think coalition or minority governments probably are not the worst thing ever, but even here we are not seeing mass swings in policy every time we go from Conservative to Liberal.