All I've heard (and I think it was discussed here last year) was that LCY had said they were obviously aware of the need for another heliport and that they were seeking some land outside their current boundary to see if they could build a site.
However, land (even horrible old sewage farm land) down that way is now getting £1.25m an acre.
And residential or industrial is going to generate a better return than a heliport.