I'm not so sure about that, barring some major disaster or scandal then I'd say that there looks like a slight Indy majority in Holyrood for the foreseeable future and slight is enough. That's not nailed on and there is always the danger of the electorate simply getting fed up of the current government and fancying a change - but there needs to be a credible alternative and I'd argue there isn't one or likely to be one. That's all dependent on support for Independence remaining at the same level it has since September 2014 and that being the primary determining factor of how people vote in Holyrood elections. Neither of these look like changing any time soon over.
The Holyrood voting system actually works in favour of the SNP and Greens to an extent and works against the Unionist parties.
In 2016, the SNP constituency seats went up from from 53 to 59 on that basis you would expect the list seats to also fall - which they did - but fell further because of 2.3% reduction in the list vote. However, funnily enough the Green share of the list vote went up by 2.2% - which could only be a swing from SNP to Greens - but that was enough for them to pick up an additional 4 list seats and so meaning there was an Indy majority with 69 seats down slightly from 72 (including Margo) in 2011.
The problem for the three Unionist parties is two fold. Firstly, they are almost obligated to contest every constituency and even if they put up paper candidates they are still competing with each other, the Greens however aren't as constrained and can focus mainly on the list, where - because of the dominance of the SNP in the constituencies - they can pick up seats usually at the expense of Labour, Tory or Lib Dems.
Secondly - one benefit that the SNP has is that they don't need to concern themselves about the UK dynamic in respect of how they conduct campaigns in Scotland. For Labour and the Tories while they might be in tune on the constitution they are diametrically opposed on almost everything else and I'd say that with a Corbyn led party, that is gap is even further.
In 2016, the Conservatives wanted to talk about *nothing but* than the constitution, Labour wanted to talk about *anything but* it. The problem is though that while the constitution remains the defining question in Scottish Politics, they are both fishing in the same pool for votes which is to the SNP's advantage where the constituency votes are concerned.