If it's that they want then surely it would be easier & cheaper to just stroll around regents park? People go to the zoo to see animals that they can't see in their local park or woods! At the risk of repeating what i've said in the past, London really should make better use of the limited space it does have, the mappins, the offshow Clore, large areas underused on both sides of the canal are unacceptable. There is no point in having a nature walk or bird watching in a zoo located in a massive public park either. Everyone i speak to who has visited in the last 5 years after a gap of 20 plus years is totally underwelmed by the experience. It saddens me that when people ask me to recommend a zoo, i avoid suggesting London, unless its during winter when the indoor areas make it more competitive.
I'm sure it's on their to do list. Things take time and money. It seems to be one MAJOR project every couple of years but I don't reckon that will be their next major project.