Small network over 2 buildings upgrade design

Hello, we have a small network with 2 buildings. At this time:

- the Main Building, with the main data center and 5 floors. Each floor with its 1G access switch. They go directly to the Core switch (a stack with 2x 48 10GBASE-T ports). Core switches receive all connections in the data center (3xESX, 2xSAN, access switches, firewalls, routers). There is a 2x10 SFP+ fiber connection to the second building. The core is the router for all VLANs on the network. There are VLANs that spread over all the buildings (wifi, video, servers, storage,...)

- second building: there is a 3xcisco 3750 stack that receives all client connections and connects to the CORE. We recently added a 10GBASE-T Multigigabit switch for new Wi-Fi access points and for a 2xESX connection and a SAN for remote backup and possible disaster recovery from the main data center. At the moment there is no L3 in this building (we could manually enable it with static routes if necessary).

Now we are going to update the whole network and we are thinking about the design. We have new requirements:

- 10G / 25G Fiber / Dac connection in the main data center for new servers and SAN (but still need to maintain 10GBASE-T connections)

- We have to anticipate 10G fiber / DAC ports in the backup data center

- Multi-gigabit wifi access points

- Digital audio and video over the network

- Capacity for next 7 years

I was thinking in a design like:

- Main building:

• multigigabit access switches with 10G uplinks to the core
• Core like a leaf and spine:
  
  • Leaf: 10GBASE-T pair of stacked switches. It could be the L3 router of the entire network. Uplink to second building at 40G / 100G
  • Spine: L2 10G / 25G pair of stacked fiber switches for new servers and SANs. 40G / 100G Leaf to core connection
    

- Second building:

• -Stack of 3x Multigigabit access switches
• 2x 10G fiber switches connected to the multigigabit stack. The uplink to the core could be from these switches or from the Multigigabit stack.

What you think? Suggestions? Anything to consider?

Thanks