Yes and yes.
Elusive Spellfist's ability will resolve before Dance of the Skywise, so it will have gained +1/+0 and will not be able to be blocked. It will not lose either effect because power/toughness modifiers are applied after base power and toughness changes in the layers, and because "unblockable" is not an ability, but rather a change to the rules governing the permanent.
Battlewise Hoplite's heroic ability will resolve before Dance of the Skywise, so as above the power/toughness modifier from the +1/+1 counter will remain even after base power and toughness are changed.
April 8, 2015 12:11 a.m.
Those are both correct. The "Can't be blocked this turn" which the Spellfist has isn't an ability, so the Dance doesn't take it away. Since Dance's power and toughness setting apply before any effects which modify power and toughness the +1/+0 until end of turn (and the +1/+1 counter) continue to apply.
April 8, 2015 12:13 a.m.
@raithe000: It's worth noting that the order of resolution doesn't matter here because the P/T changes are applied in different layers.