Let me give you some information than
We presume that there will be 3 clusters: Olympic Park, Old City and Ataköy Cluster. Taksim might be called downtown because it will be the main hotel area. Olympic Village will be in Olmypic Park btw. There is no "real" downtown in Istanbul. Because it is so huge there are like 5-6 main centers in the city. But Taksim is the main connection point of everything, it is like the heart of the city.
This is the main map: At the top Olympic Park, in the very south Ataköy and Old City just next to it. Taksim is just on the right close to Golden Horn.
Olympic Park-Taksim: 26,4 kms this two centers are already connected with light rail and tram. Olympic Park metro will be finished at the end of this year.
Olympic Park-Ataköy: 18 kms and these two has direct connections with light rail, metrobus and suburban rail
Olympic Park-Old City: 20 kms this cluster has also rail, metro and tram connection with main center.
Ataköy - Taksim: 18 kms
Old City - Taksim: 5 kms
Three clusters and main hotel area(Taksim) all have rail system which is connected to each other. They are developed right now with new lines. Rail system was not developed like this at our last bid.
Ataköy-Old City: 16 kms and there is direct rail system connection
you can see page 20 of this thread I posted a detailed infastructure plan of Istanbul and also some venues.
also there will be a new highway at the very north of the city which will be the expansion of Third bridge in the north. This highway was planned to use as Olympic Lane in our 2008 plan.