It is always a minefield attempting to predict the supply and demand curves into future dates. There are simply too many variables that can come into play. However, if you take a broad brush approach and temper it with cautionary caveats, there are some reasonable assumptions.
There is almost certainly going to be a significant expansion of the MPL programmes, and to that end, and based on forecast projections, all of the airlines that are currently offering them are likely to continue doing so for the foreseeable future. These airlines are also likely to be joined by others who already run non-MPL cadet programmes.
Non-MPL cadet programmes run in conjunction with the larger FTO's who specialize in this training, are likely to grow in response to commercial demand from both their existing customer base, and new customers, although it is inevitable that much of this demand will gradually switch over to MPL as this is likely to be the growth market in the future.
Certainly in the case of the airlines you have mentioned, it is very likely that these programmes will continue to represent a significant part of their recruitment demand for the future, and given growth in their markets, the relative proportion of that recruitment demand is also likely to increase. As already mentioned, the methodology is likely to evolve towards the new competency based training regimes in relevant airline environments (MPL,) at an accelerating rate.