It is possible to have 2gbps or even 10gbps. However, the equipment and setup would be expensive (both network and computer would need to support 10gbps). For example, for VQ, their 2gbps plans either supports a multi (1+1 gbps) or single network (2 gbps).
By doing a VLAN on a 1gbps plan, the maximum would still be 1gbps.
However, on the plans such as MR 1+1, or VQ/ST 2gbps plans, you would allow a maximum speed of 2gbps across the different ONT ports. Meaning to say computer A and B if connected on different ONT ports can each reach a maximum of 1gbps without sharing bandwidths with one another.
Honestly, for most users, as long as it is a fibre connectivity (even with very low speeds of 100mbps), it would already be more than sufficient. Considering a 2gbps (or 1+1) would already be a way overkill.