Hello Sameer,
it may be wise to post this under data center forums.
personally I had no chance to work on a Nexus up to now.
Second hand information got from people that has took part in cisco presentations has noted that the weak point are the extenders, the 2000 series that have some limitations that make them difficult to use in some server farms.
but no direct experience.
The most important limitation that has been reported in that presentation is the fact that you cannot build a bundle of more then two ports on the downlink ports. And that at the time of the presentation was not possible to form bundles that extend over multiple extenders
This can be a big problem because most modern servers have a lot of GE NICs and some designs use bundle of 4 GE ports.
For example last servers that are installed in our serverfarms have 7 or 14 GE ports with different use, and server people asks for 4 GE bundles with trunk.
For this reason our design group is thinking of using C4948 instead of the extenders for the design of new server farms.
Your design looks like reasonable. Nexus 2148 is declared capable to connect with 4 tengiga to parent switch
The Cisco Nexus 2148T has 48 1000BASE-T Ethernet host interfaces for its downlink connection to servers or hosts and 4 10-Gigabit Ethernet fabric interfaces with SFP+ interface adapters for its uplink connection to the parent switch.
http://www.cisco.com/en/US/docs/switches/datacenter/nexus2000/sw/configuration/guide/rel_4_1/Cisco_Nexus_2000_Series_Fabric_Extender_Software_Configuration_Guide_chapter2.html#con_1197795
Also configuration looks like correct per nexus extender configuration guide
Hope to help
Giuseppe
