My current home heating is through a natural gas forced air furnace. I have tried to get quotes from multiple contractors.. all of them basically keep saying that I need a backup natural gas furnace any way because of the blower assembly in furnaces. Basically, even if I install a heat pump (ducted) I still need to replace my old furnace with a new one.
Depends on how old and cruddy the heat pump design they're offering is.
Technology Connections covers this in their heat pump series. The old-guard American makers like Trane and Lennox are not happy about the heat pump revolution, and want to stretch a couple more years out of the factories that make That 70's Air Conditioner.
They have heat pump offerings to satisfy the government (sort of like the way Dodge would begrudgingly offer the Dodge Neon but they'd much rather sell a Ram Truck). But they deliberately make their lines either cruddy or wildly overpriced, so their sales reps can present a "good - better - best" spectrum to customers. Every contractor I've talked to would really, really rather you get the cheapest 14 SEER non-reversible air conditioner and a gas furnace. In their marketing plan, The real purpose of the "better-best" tiers are to fleece money from the richer folks, and to the rest, convince you to go with the "good" tier.
Meanwhile, makers of Asian style systems like Hitachi or Pioneer sell "best" right out of the chute. That heat pump series covers the Chicago-ready capability of these units in video 2.
So the information you're hearing is dated, and domestic A/C industry propaganda. It's designed make you lament that since "nobody" makes a cold-weather heat pump, you might as well just go with a gas furnace and That 70's Air Conditioner.
That said... I do think a gas furnace is worthwhile, but I feel strongly it should be an entirely electricity-free, Empire-style gravity (convection) wall or floor furnace. Why? Blackouts. The worst nightmare with a forced-air furnace is the need to run a generator simply to circulate air so the heat can work. These work just fine. You set their simple mechanical thermostat below the working range of your regular thermostat, and they kick on when the system fails. They're only in the 70-80% efficient range since they use convection for exhaust air, but you only need them during emergencies.
"Can heat pump completely replace natural gas furnace" Generally yes but maybe no. If your ambient temperature goes below freezing outside probably no. If the outside never goes below freezing probably yes. I put my system with a backup gas furnace instead of electric heating coils. This has turned out to be a good idea as the cost of electricity has gone up dramatically. I just run it on emergency heat (gas heat) and it saved a lot more on the electric bill then the gas used. Earlier when I installed it the heat pump was the most cost effective.