Ripple's XRP, Dogecoin (DOGE), and Polkadot (DOT) are highlighted as key altcoins to watch this December. XRP is gaining traction due to its strategic bank partnerships and the recent launch of the RLUSD stablecoin. Meanwhile, Dogecoin maintains its popularity through cultural appeal and ongoing development efforts. Polkadot is advancing with significant upgrades and its sophisticated multi-chain technology, positioning it for future growth. These projects are noted for their robust technology and potential for long-term expansion.