Natal is probably the best hope they have left. currently they cannot drop the arcade price much, the console still costs probably more than 100$ to make so with shipping and everything else i guess 149$ might be possible to do.
only way they can go below that will be a new hardware revision with less chips (integrating cpu+gpu+ memory), this will only work in a smaller production process like 45nm or 40nm (else chip will be too big and too hot to be any use). there has been rumors ms is preparing for this, but since TSMC had big troubles with 40nm till now i doubt such a revision will launch before late this year. so might as well ship a new slim x360 together with natal.
Price cuts are another option, but as we all have seen they are also most effective when done closer to hoilday season.
so my guess for ms strategy this year would be that they won't do much till late summer, and then try a heavy marketing initiative for holiday season with price drops, slim version and natal. when using all 3 cards at once this will give them a quite good position for the holiday season, much better than if they split these things out over the year.