I think we've had measurements from multiple separate images by folks who are confident in their skills and the verdict seems to be around 18 metres. Of course its a matter of wait and see. It may not even be 054B, but something else (granted, few candidates come to mind).
PS: its also worth noting a wider beam does not necessarily constitute a hull overall larger than 052DL for example. But ASW frigates tend to have wider hulls to ensure enough space for dampening and isolating equipment more than eg on a multirole or AAW hull. Take for example British Type 26, which has a whopping 20 metre beam, about what 055 has. Constellation class also nudges towards 20 metres.
I would want to add that the trend of wiser surface combatant beams is a modern recent trend we've seen across multiple categories of surface combatants (frigates, destroyers), and isn't necessarily exclusive to ASW oriented ships.
For example, there are legacy ASW surface combatants with much narrower beams, such as Type 23 frigate.
The growth in beam among these categories of ships comes alongside a general growth in dimensions and overall displacement (and one could argue, a shift in role and mission scope and endurance expectations) for modern combatants.
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In any case, it is already largely accepted that 054B will be somewhat larger than 054A, and there are already some longstanding accepted rumours as to what various subsystems it will have which dovetail with some of the size that's been thrown around for it.
The questions we have left about its size and dimensions, is just whether it does legitimately have a wider beam than the 054/A which would mean it is a new hull entirely.
In which case, assuming the 054B designation does hold, will be very useful for us as it means that at last we can recognize that the "05X" type/class system is not sacred and doesn't necessarily correspond to propulsion or hull lineage at all.