Will Bitcoin (BTC) reach $100,000 by December 31, 2026? Current price ~$64,000. Required gain: +56% in ~5.5 months. Key factors: (1) ETF cumulative inflows $58.7B as of May 2026, total AUM near $100B; (2) BlackRock IBIT and Fidelity FBTC dominating; (3) April 2024 halving now 15 months past - historically bullish 12-18 month window; (4) Fed policy uncertainty; (5) Institutional adoption accelerating per Grayscale 'Dawn of Institutional Era' report. Analyze probability with bull/base/bear cases.

The strongest counterargument is the seasonal cycle timing: December 2026 falls in the post-peak drawdown zone, and BTC has historically lost 65-84% from cycle peaks. If BTC peaks at $150K in mid-2025 and draws down 65%, it would be at ~$52.5K by December 2026 — well below $100K. However, I revise toward support because: (1) $100K requires only a 56% gain from $64K, which is modest even in a diminished cycle; (2) ETF institutional flows ($58.7B cumulative, ~$100B AUM) create a structural demand floor that didn't exist in prior cycles, likely compressing drawdowns from 65-84% to 40-55%; (3) even with a 50% drawdown from a $180-200K peak, BTC lands at $90-100K — right at the $100K threshold. The ETF-driven demand floor makes $100K at year-end 2026 more likely than not, though not by a wide margin.

Breaking into components: (1) Halving cycle — we're in the 12-18 month bullish window where 3/3 prior cycles delivered 700%+ gains; (2) ETF flows — $58.7B cumulative is unprecedented institutional demand, creating structural bid; (3) Probability math — 56% gain in 5.5 months is only ~0.5 standard deviations given BTC's volatility, implying ~69% probability of occurrence if drift is neutral. However, diminishing halving returns and Fed uncertainty cap confidence below 0.70. Base case: $95-105K range by year-end.