ARM will grab the most share in the low-cost laptop business where price is a more important purchase consideration than performance. So while Intel will lose market share by units, the cut into its share by revenue will be much smaller.
Although in a couple of years the multiple core Arms chips are likely going to compete fairly well on performance as well.
And that assumes Intel's continuing efforts to drive down the power consumption of its processors doesn't allow it to deliver chips that provide better performance at a comparable price and power draw as ARM offerings.
Unlikely - Arm designed from ground up as low power. Intel, constrained by X86 have no such option. Arm more likely to catch Intel performance at low power, than for Intel to catch Arm in the low power high performance category.