This is simply impossible in practice, but if you want to talk about what would happen in theory, then the price would basically be a flat line. If you want to see how that would look like, just look at a dead exchange graph for example BTC-E:
https://bitcoinwisdom.com/markets/btce/btcusdAs you see, it's a perfect flat line. This is impossible, because equilibrium never happens in markets, unregulated ones at least, as there is always some buying and selling action.
I agree that everyone electing to HODL is impossible in practice but I don't share the point of view that it would culminate in a flat line in theory, because two scenarios are possible:
1. if Hodlers are unwilling to sell, the coin would become scarce and buyers will naturally bid up the price;
2. if Hodlers are willing to sell, but no buyer is willing to buy, that's where there's a problem, if not a threat.
