Note that centralizing all BES servers into a location and connected to a single SQL server is a good idea if and only if all servers are local. For e.g. All BES, mail servers, remote BAS, remote BMS and SQL are all in US. Or All BES, mail servers, remote BAS, remote BMS and SQL are all in India.
Note that BAS must not have a latency of >20ms with SQL server. Similarly, the lesser latency between BES and mail servers are critical.
See some potential issue: Knowledge Sharing - Pending internal events + reconciliation events count increasing
Remember the golden rule of placing BES near mail servers + SQL server. You don't want latency due to bad geograhical setup to ruin your BlackBerry services. Good time to consolidate, planning properly can save you a lot of time after your BES 5.0 roll out.